Explicitly require rooted device in `mojo_test`.

mojo/devtools/common/devtoolslib/android_shell.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import atexit
 import hashlib
 import json
 import logging
 import os
 import os.path
@@ skipping 181 matching lines @@
       self.adb_running_as_root = False
 
     return self.adb_running_as_root
 
   def _is_shell_package_installed(self):
     # Adb should print one line if the package is installed and return empty
     # string otherwise.
     return len(subprocess.check_output(self._adb_command([
         'shell', 'pm', 'list', 'packages', _MOJO_SHELL_PACKAGE_NAME]))) > 0
 
-  def check_device(self):
+  def check_device(self, require_root=False):
     """Verifies if the device configuration allows adb to run.
 
     If a target device was indicated in the constructor, it checks that the
     device is available. Otherwise, it checks that there is exactly one
     available device.
 
     Returns:
       A tuple of (result, msg). |result| is True iff if the device is correctly
       configured and False otherwise. |msg| is the reason for failure if
       |result| is False and None otherwise.
@@ skipping 14 matching lines @@
     if len(device_list) > 1:
       return False, ('More than one device connected and target device not '
                      'specified.')
 
     if not len(device_list):
       return False, 'No devices connected.'
 
     if not device_list[0].endswith('device'):
       return False, 'Connected device is not available.'
 
+    if require_root and not self._run_adb_as_root():
+      return False, 'Cannot run on an unrooted device.'
+
     return True, None
 
   def install_apk(self, shell_apk_path):
     """Installs the apk on the device.
 
     This method computes checksum of the APK and skips the installation if the
     fingerprint matches the one saved on the device upon the previous
     installation.
 
     Args:
@@ skipping 171 matching lines @@
           Results.output = rf.read()
 
     run_thread = threading.Thread(target=do_run)
     run_thread.start()
     run_thread.join(timeout)
 
     if run_thread.is_alive():
       self.stop_shell()
       return None, Results.output, True
     return None, Results.output, False